Female athletes, in particular soccer players, suffer concussions at a "significantly higher" rate than their male counterparts, according to a study released this month by the American Academy of Orthopaedic Surgeons.

In matched sports, girls were 12.1 percent more likely to sustain a concussion than boys, according to the report, which tracked concussions in a sport relative to total number of injuries from 2005 to 2015 using the High School Reporting Information Online injury surveillance system. In basketball, for example, concussions only accounted for 8.8 percent of boys' injuries, but 25.6 percent of girls' injuries.

"The neck muscles of girls just aren't as developed as boys are," said Wellington Hsu, one of the study's authors and a professor of orthopedic surgery at Northwestern. "So if girls experience an impact, it makes sense they might be affected by it more than boys if they don't have the muscles to cushion that impact."

Researchers from Northwestern University and Wake Forest University studied data from football, soccer, basketball, wrestling and baseball participation for boys; soccer, basketball, volleyball and softball for girls.

The results showed a striking gender-based difference in the incidents of concussion. Football, a sport most typically associated with brain injury but also has a high number of total injuries due to its being a collision sport, was fourth on the list of concussion as a percentage of total injuries, behind girls' soccer, girls' volleyball and girls' basketball.

"We were surprised at how the incidence of concussions particularly in girls over the past five years has increased," Hsu said. "And we found that sports that weren't typically linked to concussion are actually quite risky."

The study's authors attribute that increased risk to a lack of protective equipment available for female athletes and an increased emphasis on physical play. In soccer specifically, the authors cite a potential increase in headers, and wrote, "It remains unclear why boys soccer players do not appear to have the same risk as girls."

"We've seen a lot of data come out of women's soccer that shows the women may very well be playing harder than the men," said Geoff Manley, chief of neurosurgery at Zuckerberg San Francisco General Hospital and co-director of the Brain and Spinal Injury Center at the University of California-San Francisco.

"These are tremendous athletes with incredible skill who play really hard," he said. "And there is no protection."